Fix issue 12023 by avoiding a critical edge in the SSA graph with a switch statement.

sdk/lib/_internal/compiler/implementation/ssa/codegen.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of ssa;
 
 class SsaCodeGeneratorTask extends CompilerTask {
 
   final JavaScriptBackend backend;
 
@@ skipping 682 matching lines @@
     js.Expression key = pop();
     List<js.SwitchClause> cases = <js.SwitchClause>[];
 
     js.Block oldContainer = currentContainer;
     for (int i = 0; i < info.matchExpressions.length; i++) {
       for (Constant constant in info.matchExpressions[i]) {
         generateConstant(constant);
         currentContainer = new js.Block.empty();
         cases.add(new js.Case(pop(), currentContainer));
       }
-      if (i == info.matchExpressions.length - 1 && info.hasDefault) {
+      if (i == info.matchExpressions.length - 1) {
         currentContainer = new js.Block.empty();
         cases.add(new js.Default(currentContainer));
       }
       generateStatements(info.statements[i]);
     }
     currentContainer = oldContainer;
 
     js.Statement result = new js.Switch(key, cases);
     pushStatement(wrapIntoLabels(result, info.labels));
     return true;
@@ skipping 2270 matching lines @@
   if (leftType.canBeNull() && rightType.canBeNull()) {
     if (left.isConstantNull() || right.isConstantNull() ||
         (leftType.isPrimitive(compiler) && leftType == rightType)) {
       return '==';
     }
     return null;
   } else {
     return '===';
   }
 }